Hybrid manual-electronic pipette

ABSTRACT

A hybrid manual-electronic pipette combines a manually driven piston with real-time electronic measurement of liquid volume and piston displacement while compensating for both pipette-specific and pipette model-specific variations. The hybrid nature of the pipette facilitates increased accuracy and improved ease of use, and enables additional functionalities not practicable with traditional manual pipettes.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.11/906,187 filed on Sep. 27, 2007 and entitled “HYBRID MANUAL-ELECTRONICPIPETTE,” which claims the benefit under 35 U.S.C. Section 119(e) ofU.S. Provisional Application No. 60/947,367, filed on Jun. 29, 2007 andentitled “HYBRID MANUALLY-OPERATED PIPETTE WITH ELECTRONIC VOLUMEMEASUREMENT,” which is owned by the assignee of the present inventionand is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to volume adjustable manual pipettes and,more particularly, to a manually-operated pipette equipped with anelectronic piston position sensor and user interface.

U.S. Pat. No. 3,827,305 (“the '305 patent”) describes one of theearliest commercially available digitally adjustable air displacementpipettes. To provide for volume adjustment, the pipette includes athreaded shaft extending through a fixed nut. Manual turning of theshaft produces axial movement of a stop member for limiting axialmovement of a plunger to define a volume setting for the pipette. Thevolume setting is displayed on a mechanical micrometer displaycomprising a series of indicator rings each encircling the threadedshaft.

U.S. Pat. No. 4,909,991 describes a later commercially available singlechannel manual pipette manufactured by Nichiryo Co. Ltd., Tokyo, Japan.The Nichiryo pipette includes an elongated hand-holdable housing for anupwardly spring biased plunger. An upper end of the plunger extendsabove a top of the housing and carries a control knob for thumb andfinger engagement in manually turning the plunger and for axially movingthe plunger in the pipette housing between an upper stop and a lowerstop at which all liquid within a tip secured to a lower end of thehousing is expelled by the downward movement of the plunger. The upperstop is axially adjustable within the housing in response to a turningof a hollow volume adjustment screw or shaft keyed to the plunger. Theaxial adjustment of the upper stop adjusts the volume of liquid that thepipette is capable of drawing into the tip in response to upwardmovement of the plunger to the upper stop. The pipette also includes alock mechanism including a lock knob for locking the plunger againstrotation to thereby set the upper stop in a fixed position and hence setthe volume adjustment for the pipette.

In pipettes such as these, the volume setting is typically read from astacked series of indicator rings, each bearing the digits from zero tonine. The least significant (usually bottom-most) ring is coupled to theposition of the volume adjustment screw, and is calibrated such that asingle-unit change in the pipette volume (as defined by the position ofthe upper stop) will be reflected by a single-unit change in the digitshown on the coupled ring. The remaining rings serve as counters oftens, hundreds, or thousands of the increment shown in the leastsignificant ring.

Now, more than thirty years after volume indicator of the '305 patentmade its initial appearance, the most common manual pipettes still usemechanical volume indicators very similar in operation to the onedisclosed therein. It will be appreciated, however, that mechanicalvolume indicators such as these have several shortcomings. Amechanically coupled indicator will have some degree of slack, orbacklash, resulting from the linkage between the screw that sets theupper stop and the displayed digits. If a user turns the screw in onedirection to reach a desired setting but overshoots, it may be difficultfor small adjustments in the opposite direction to be registered in thevolume indication because of this effect. Moreover, with strictlymechanical arrangements such as the one disclosed in the '305 patent, itis difficult to accurately compensate for any nonlinearities present inthe volume settings, for example at very small volumes compared to thetotal capacity of the pipette, even when those nonlinearities are knownin advance and consistent across a manufactured lot of pipettes. Andwhen non-linearities are inconsistent and arise from manufacturingvariances, it is nearly impossible to compensate fully with a mechanicalapparatus.

U.S. Pat. No. 6,601,433 describes the commercially available “Ovation”pipettes sold by Vistalab Technologies, Inc. In these pipettes, and asdescribed in the patent, the volume adjusting upper stop is positionedby an electric motor drive mechanism with a digital control. The digitalcontrol enables calibration of volume settings, but because there is noelectronic sensing of the manually operated plunger position, theprecise position of the plunger cannot be ascertained at any given time,and accordingly, accurate calibration of the volume adjusting upper stopmight not always be reflected in the results of using the pipette.Moreover, the motor drive apparatus imparts unnecessary complexity tothe device and requires a significant amount of power to operate, andconsequently, reasonably capacious batteries are also needed. Both themotor drive and the batteries add size, weight, and considerable expenseto the pipette.

PCT Publication No. WO 2005/093787 A1 describes the “Ultra” Pipetteavailable from Gilson, SAS, of Villiers le Bel, France. The Gilson Ultrapipette uses conductive tracks and corresponding contact brushes to sendsequences of pulses to a microprocessor when the volume adjustment screwis turned. In this manner, by counting pulses, the microprocessor canidentify when the adjustment screw is moved either up or down, and basedon prior position information a new position can be calculated. But as aresult of this design, the microprocessor cannot determine the absoluteposition of the stop with no prior data. If power is removed or amalfunction occurs, the volume reading must be recalibrated by movingthe adjustment screw to a known position and resetting the pipette, andas with traditional pipette adjustment mechanisms, it can take manyturns of the screw to accomplish this. Moreover, the brush-on-trackencoder design is susceptible to wear and unreliability over the courseof time, and because the encoder is mechanically linked to theadjustment mechanism, slack and backlash can occur.

Other volume adjustable manual pipettes with electronic digital displayshave been developed and are disclosed in U.S. Pat. Nos. 4,567,780;4,763,535; and 5,892,161.

For a more complete understanding of the current state of the artrelative to the volume adjustability of manual pipettes, each of theabove-identified patents is incorporated by reference into thisapplication.

U.S. Pat. No. 6,428,750 issued Aug. 6, 2002 to the assignee of thepresent invention, and U.S. Pat. No. 7,175,813 issued Feb. 13, 2007 alsoto the assignee of the present invention, describe an improved volumeadjustable manual pipette having a quick set volume adjustment mechanismand a plunger position sensor. The volume setting of the pipette ismonitored by the sensing and control circuitry to provide a real timedisplay of the volume setting of the pipette on the electronic digitaldisplay. While the quick set and volume display features represent aconsiderable advance in the art of manual pipettes, the describedpipette does not contemplate enhanced pipetting functionality beyond theability to quickly change volume settings, or improved calibrationtechniques reducing the likelihood of mechanical slack or unreliabilityto affect the utility of the pipette.

There is a continuing need for a volume adjustable manually operatedpipette including an accurate and highly visible display of pipettingvolume. A pipette capable of measuring the position of a manually drivenplunger unit, calibrating that measurement, and displaying the positionin real-time meets this need, and the real-time measurement,calibration, and display would enable enhanced functionality overtraditional manually operated pipettes.

SUMMARY OF THE INVENTION

Accordingly, a manually operated pipette according to the inventionaddresses the shortcomings of presently commercially available handheldpipettes, and adds additional functionality not practicable usingtraditional manual pipettes.

One embodiment of a hybrid manual-electronic pipette according to thepresent invention comprises a plunger mounted for manual movement in ahousing to and from a stop to aspirate a fluid into and dispense thefluid from a tip extending from the housing. The pipette is furtherprovided with a real-time electronic sensor, a low-powermicrocontroller, and a simple yet flexible user interface.

The electronic sensor permits the position of a piston to be sensed andcommunicated to the user in real time via a user interface. A processorintegral with the pipette allows various calculations to be performed onthe piston position, including the advantageous use, communication, andmanipulation of liquid volume measurements, pipetting techniqueanalysis, use observation and auditing consistent with preferredlaboratory practices, performance optimization, calibration offsets,multi-point non-linear calibration, and cycle counting.

It will be noted that manual pipettes have continued to be popularsystems of choice due to their lower cost and ultimate control that theuser has in choosing how to manually push the plunger down. Manualsystems however lack any form of feedback in terms of exactly where theplunger is positioned and hence the actual volume being aspirated ordispensed.

The hybrid pipette according to the invention represents an advancementin manual pipette development that retains the control and feel of atraditional, ergonomic manual pipette with the addition of being able todetermine the exact position of the plunger and display this to theuser. This technology enables an LCD to display, in real time, thevolume that is being aspirated or dispensed by the pipette.

Real time position sensing is a well known technology associated withmany industrial systems. Common industrial applications include controlsystems, robotics, machine tools, and measurement equipment. Besidesindustrial applications position sensing is often used in automotivesteering, braking and throttle systems. In many laboratories, equipmentposition sensing can often be found in pump systems and in thepositioning mechanisms of larger liquid handling robot systems.Heretofore, such sensing capabilities have not been advantageouslyemployed in low-cost handheld pipettes.

In a hybrid pipette according to the invention, the real timepositioning sensor is used to monitor the precise position of thepiston, and therefore the plunger. The position of the plunger/piston,which relates directly to an associated liquid volume, can be displayeddirectly on the LCD. Current manual pipettes with electronic readoutsgenerally monitor the position of the upper stop but cannot tell theuser where the plunger (or piston) is positioned.

This real time sensing of the piston/plunger in a hybrid pipetteaccording to the invention gives rise to a number of unique featuresthat currently have been unavailable in any manual pipette.

A hybrid pipette according to the invention can display the amount ofliquid being aspirated into the pipette tip or it can display the amountof liquid being dispelled from the tip. Accordingly, a user of a manualpipette can perform tasks like titrating, diluting, multi-dispensing andmeasuring an unknown amount of liquid.

A hybrid pipette according to the invention can determine whether anacceptable pipette technique is being used by sensing whether a samplehas been blown out correctly or if plunger movement is too rapid. Thiscan be very beneficial for teaching new users.

With electronic memory, the pipette can alert the user to when the nextscheduled service is due, providing a unique GLP function in a manualpipette.

The real time sensing capability in a hybrid pipette according to theinvention allows multiple calibration and compensation functions to beused (like the EDP-1 and EDP-3 Electronic Pipette families from RaininInstrument, LLC, of Oakland, Calif.) as opposed to a single offset asused in standard manual pipettes. In an embodiment of the invention, apiston position correction function, a volume correction function, andan optional user calibration function can all be employed to improve orcustomize the performance of the pipette.

Moreover, the real time sensing in a hybrid pipette according to theinvention allows for a real pipette cycle counter to be used. The cyclecounter in not simply counting plunger depressions but only counts apipetting cycle if a complete pipette cycle has been observed withouterrors.

In a pipette according to an embodiment of the invention, an axiallymoveable volume setting member in the housing defines the stop and avolume setting for the pipette and is axially moveable by a userturnable volume adjusting member. The plunger is coupled to an airdisplacement piston and a highly accurate and reliable electronicposition sensor component, which in turn allows measurements to beprovided to a low-power microcontroller and display, thereby enablingreal-time feedback on the position of the plunger, calibration of volumesettings based not only on the position of the volume adjusting stop butalso on the actual position of the plunger and the air displacementpiston, and numerous enhanced pipetting functionality modes andcapabilities not practicable with traditional fully mechanical pipettesor current state-of-the-art manual pipettes with electronic displays.The direct and tight (i.e. substantially free of slack) coupling of theplunger to the air displacement piston and sensor component eliminatesmechanical backlash, while the microcontroller and user interfacefacilitate increased utility and ease of use. Multiple calibrationfunctions permit the highly accurate and precise operation, bycompensating not only for position sensor signal variations from pipetteto pipette, but also for the non-linear but relatively invariantphysical characteristics of small volumes of liquids and how theyinteract with the liquid end of a pipette.

Accordingly, then, a hybrid manual-electronic pipette according to theinvention includes a manually-operated piston and an electronic pistondisplacement sensor coupled to the piston, a fluid-tight liquid end witha distal opening permitting fluid to be picked up or discharged throughthe opening in response to movement of the piston within the liquid end,and a processing unit. The pipette includes a memory subsystem capableof storing data records representative of how the pipette has been used.In an embodiment of the invention, the pipette is capable oftransmitting these data records to external equipment via a data link.

As described herein, the invention is particularly applicable toair-displacement pipettes, though it should be noted that the structuresand functions described herein are also applicable topositive-displacement pipettes.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features, and advantages of the invention willbecome apparent from the detailed description below and the accompanyingdrawings, in which:

FIG. 1 is an external view of a hybrid manual-electronic pipetteaccording to the invention, with a disposable tip mounted to a liquidend of the pipette;

FIG. 2 is an enlarged external view of the hybrid manual-electronicpipette of FIG. 1, illustrating the functionality of a volume-settingmechanism according to the invention;

FIG. 3 is a simplified external view of the hybrid manual-electronicpipette of FIG. 1;

FIG. 4 is a schematic view illustrating a rigid linkage between aplunger assembly and a sensor assembly of the pipette of FIG. 3;

FIG. 5 is a schematic view illustrating a portion of the pipette of FIG.3 with a plunger assembly in a released position against an upper stop;

FIG. 6 is a schematic view illustrating a portion of a pipette of FIG. 3with a plunger assembly in a partially-depressed home position;

FIG. 7 is a schematic view illustrating a portion of a pipette of FIG. 3with a plunger assembly in a fully-depressed blowout position;

FIG. 8 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a volumesetting lock in an unlocked condition;

FIG. 9 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a capacity setto an exemplary value of 123.6 microliters;

FIG. 10 is a view of the user interface display of FIG. 9, with thepipette configured and prepared to pickup a sample of liquid;

FIG. 11 is a flowchart illustrating an exemplary sequence of stepsperformed in operating a hybrid manual-electronic pipette according tothe invention in a traditional pipetting operation mode;

FIG. 12 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with the pipette ina tracking operating mode and a volume setting lock in an unlockedcondition;

FIG. 13 is a view of the user interface display of FIG. 12 with thepipette piston in a position representing an exemplary value of 25.8microliters of capacity;

FIG. 14 is a view of the user interface display of FIG. 12 with thepipette piston in a position representing a blowout portion of adispensing stroke;

FIG. 15 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with the pipette ina titration operating mode and a volume setting lock in an unlockedcondition;

FIG. 16 is a view of the user interface display of FIG. 15 with thepipette having dispensed no fluid;

FIG. 17 is a view of the user interface display of FIG. 15 with thepipette having dispensed an exemplary quantity of 102.6 microliters offluid;

FIG. 18 is a view of the user interface display of FIG. 15 with thepipette piston in a position representing a blowout portion of atitration stroke;

FIG. 19 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a cyclecounter displayed;

FIG. 20 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a low-batterysymbol displayed;

FIG. 21 is a block diagram illustrating the major functional subsystemsof a hybrid manual-electronic pipette according to an embodiment of theinvention;

FIG. 22 is a flow diagram illustrating the steps performed in thetraditional pipetting operation mode of FIG. 11 combined with steps of atechnique analysis function in a hybrid manual-electronic pipetteaccording to the invention;

FIG. 23 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayalerting the user to a bad pickup operation identified by a techniqueanalysis function according to the invention;

FIG. 24 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayalerting the user to a bad dispense operation identified by a techniqueanalysis function according to the invention;

FIG. 25 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that the technique analysis function of FIG. 21 isdeactivated;

FIG. 26 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that the technique analysis function of FIG. 21 is activated;

FIG. 27 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that a fourth selectable Good Laboratory Practice cyclecounter is active and 37 days remain until a scheduled service is due;

FIG. 28 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that a total of 12,345 pipetting cycles have been performed;

FIG. 29 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that no user-calibration data is present;

FIG. 30 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that a user-calibration setting mode has been entered;

FIG. 31 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that a user-calibration clearing mode has been entered;

FIG. 32 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that user-calibration data is present and active;

FIG. 33 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that user-calibration data at a setpoint of 128.0 microlitersis being incremented;

FIG. 34 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that user-calibration data at a setpoint of 128.0 microlitersis being decremented;

FIG. 35 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating that entry of a user-calibration adjustment has beencompleted;

FIG. 36 is a graph illustrating an exemplary user-calibration scenariowith adjusted anchor points at 75 and 100 microliters and with anchorpoints at 50 and 150 microliters at their default positions;

FIG. 37 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating a scheduled service is due;

FIG. 38 is a view of a user interface display in a hybridmanual-electronic pipette according to the invention with a displayindicating scheduled service is due within 14 days;

FIG. 39 is a schematic view of a position sensor for a hybridmanual-electronic pipette according to the invention employing anoptical transducer;

FIG. 40 is a schematic view of a position sensor for a hybridmanual-electronic pipette according to the invention employing aninductive transducer;

FIG. 41 is a schematic view of a position sensor for a hybridmanual-electronic pipette according to the invention employing acapacitive transducer;

FIG. 42 is a flowchart representing a basic sequence of steps performedby a processing unit in a hybrid manual-electronic pipette according tothe invention;

FIG. 43 is a flowchart representing a sequence of steps performed incalculating a compensated piston position from signals received from arelative position sensor in a hybrid manual-electronic pipette accordingto the invention;

FIG. 44 is a plot of an ideal arctangent function, used to correlatesensor signals to a piston position in an embodiment of the invention;

FIG. 45 is a flowchart representing a sequence of steps performed inapplying a correction table to a measurement in a hybridmanual-electronic pipette according to the invention; and

FIG. 46 is a flowchart representing a sequence of steps performed inanalyzing a user's pipetting technique in a hybrid manual-electronicpipette according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described below, with reference to detailedillustrative embodiments. It will be apparent that a system according tothe invention may be embodied in a wide variety of forms. Consequently,the specific structural and functional details disclosed herein arerepresentative and do not limit the scope of the invention.

Referring initially to FIG. 1, an overview illustration of a hybridmanual-electronic pipette 110 according to the invention is presented.In general configuration, the hybrid manual-electronic pipette 110 issimilar to a traditional pipette, in that a user grips a handheld body112 of the pipette 110 and manipulates a spring-loaded plunger button114 to control the intake and discharge of fluids through a disposabletip 116, which is coupled to a liquid end 118 of the pipette 110.

As in traditional “air displacement” pipettes, the plunger button 114operates a piston configured to displace air within the liquid end 118;movement of air causes a corresponding movement of a liquid, provided anair-tight seal is present between the tip 116 and the liquid beinghandled, between the tip 116 and the liquid end 118, and between thepiston and a seal (as illustrated in FIG. 4 and described below).

The hybrid manual-electronic pipette 110 further includes a tip ejector120 mounted for longitudinal movement over the liquid end 118 andcoupled to a tip ejector button 122. After the tip 116 is mounted to thepipette 110 and used, it can be ejected and disposed of by depressingthe ejector button 122; this functionality is again comparable to thefunctionality of traditional pipettes.

Where the hybrid manual-electronic pipette 110 begins to differ fromtraditional handheld pipettes, however, is in the presence of a userinterface 124 including an electronic display 126 and button panel 128.In the pipette 110 according to the invention, the display 126 andbutton panel 128 add very little weight to the pipette, are easilyoperated, and enable improved performance and added functionality to thepipette 110 that are not generally practical with traditional pipettes.These differences will be discussed in further detail below.

As shown in FIG. 2, the user interface 124 is designed and configured tobe intuitive and easy to use. In the disclosed embodiment, the display126 is a small LCD 230, and the button panel includes a “MODE” button232, a “CC” (cycle count) button 234, and a recessed “OPTION” button 236accessible via a small opening 238. As will be discussed in furtherdetail below, the MODE button 232 is generally used to scroll throughpipette operating modes and CC button 234 operates the cycle counter.The recessed OPTION button 236 is generally used to access an optionsmenu, which gives access to advanced features and capabilities of thehybrid manual-electronic pipette 110.

The user interface further includes a piston plunger shaft 240 uponwhich the plunger button 114 is mounted, which also serves as avolume-setting knob when rotated as indicated by the arrows 242 and avolume set lock lever 244. The volume set lock lever is movable from aleft-most unlocked position 246 and a right-most locked position asindicated by an arrow 248. In the left-most unlocked position 246, theplunger button is free to rotate and change the volume of the pipette110, as in traditional pipettes, while in the right-most locked position(arrow 248) the plunger button is restricted from rotational motion(hence fixing the volume) but still permitted to be pushed by the user'sthumb to control the intake and discharge of liquids as desired by theuser. The design and operation of the locking apparatus is set forth inU.S. Pat. No. 5,849,248, owned by the assignee of the present invention,which is hereby incorporated by reference as though set forth in full.Mechanisms of this sort are commonly known.

As is visible in the simplified drawing of FIG. 3, a finger hook 310 isfurther provided to allow the user to maintain a light grip on the body112. The plunger button 114, the plunger button shaft 240, the pipettebody 112, and the liquid end 118 are all coaxial with respect to acenterline 312, thereby permitting a single linkage 410 (FIG. 4) betweenthe plunger button and the operative portion of the pipette 110 in theliquid end 118 that operates without substantial slack of backlash. And,because the mass of the pipette 110 is centered around the centerline312, and the display 126 and button panel 128 above the finger hook 310contain very little mass, the hybrid manual-electronic pipette 110according to the invention remains as easy to handle as a traditionalpipette.

The linkage 410, as illustrated functionally in FIG. 4, enables theplunger button 114 to act directly through the plunger button shaft 240to a piston 412, which maintains an air-tight seal with the liquid end118 via a seal 413. The seal 413 remains in a fixed position withrespect to the liquid end 118 and further forms an air-tight seal withrespect to an interior portion of the liquid end 118. Accordingly, asthe plunger button 114 is manipulated, the piston 412 is caused to movethrough the seal 413 and displace an air volume within the liquid end.As an orifice 150 (FIG. 1) is provided at a distal end of the tip 116,and a substantially air-tight seal is maintained at all other places,the only path for a liquid (or any fluid) to enter or exit the tip 116is via the orifice 150, and there is a deterministic relationshipbetween the volume of air displaced by the piston 412 and the volume ofliquid manipulated by the pipette 110. As will be discussed in furtherdetail below, this relationship between air displacement and liquidmanipulation is generally linear but subject to some correction.Traditional handheld manual pipettes treat the relationship as exactlylinear with a correctable zero offset.

The coaxial linkage 410 and connection between the plunger button 114and the piston 412 enables a position sensing transducer 414 to beconnected thereto, allowing the precise and specific position of theplunger button 114 (and hence the tightly coupled piston 412) to bedetermined at all times. The position sensing transducer 414 is small insize and requires very little battery power to operate. Accordingly, ahandheld manual-electronic pipette 110 according to the invention has acomparable feel to traditional manual pipettes, and any battery used topower the position sensing transducer 414 and the display 126 can bequite small. In the disclosed embodiment, a protruding portion 415 ofthe pipette body 112 (FIG. 1) between the display 126 and the fingerhook 310 (FIG. 3) houses a primary (i.e. non-rechargeable) button-cellbattery sufficient to power a hybrid manual-electronic pipette 110according to the invention for at least several months, though it willbe recognized that rechargeable batteries and other battery form factorsmay also be employed, or the pipette 110 may be powered from an externalsource.

As illustrated, the position sensing transducer 414 includes twocomponents: a sliding component 416 affixed to and moving with thepiston plunger shaft 240, and a fixed component 418 affixed to thepipette body 112. Accordingly, then, the position sensing transducer 414is able to detect and calculate the longitudinal displacement betweenthe sliding component 416 and the fixed component 418. It will berecognized that there are numerous configurations of sensing componentsthat can accomplish this function, including but not limited to avariable resistor (potentiometer), an optical sensor, a capacitivesensor, an inductive sensor, or a magnetic field sensor, some of whichare discussed in further detail below. Advantageously, mechanicalengagement and friction between the sliding component 416 and the fixedcomponent 418 are minimized, thereby reducing the likelihood of failureover time and repeated use. Moreover, there are similar advantages tokeeping the sliding component 416 passive and not directly energized,thereby eliminating the need to provide any electrical connection to themoving part, which might tend to bend, break, or otherwise fail over thecourse of time.

As in traditional manual pipettes, the plunger button 114 (FIG. 1) isspring-biased relative to two positions, namely a released and extendedposition 510 shown in FIG. 5, and a home position 610 shown in FIG. 6.With no pressure applied to the plunger button 114, a plunger spring 420(FIG. 4) biases the plunger button 114 upward against an uppervolume-setting stop, the position of which is adjusted by turning theplunger button 114 and a stop position adjustment mechanism as discussedabove. In this position, the piston plunger shaft 240 and plunger button114 are at the released and extended position 510 with respect to thebody 112 of the pipette 110 as graphically illustrated in FIG. 5.

At the fixed home position 610 illustrated in FIG. 6, with the plungerbutton 114 partially depressed, the resistance to depression of theplunger button increases. As is common in handheld pipette construction,a secondary blowout spring adds to the resistance offered by the plungerspring 418. The increased resistance is sensed by the pipette user anddefines the home position 610. Between the released and extendedposition 510 and the home position 610, only the plunger spring 420biases the plunger button position upward toward its extended position510, and a relatively light first force level is required to act againstthe spring bias. Between the home position 610 and a fully-depressedblowout position 710 illustrated in FIG. 7, both the plunger spring 420and the blowout spring act upward against the plunger button 114, and ahigher second force level is required to act against the spring bias.This configuration including a primary plunger spring 420 and asecondary blowout spring is common in handheld pipettes.

Accordingly, at the home position 610, the user feels a tactiletransition between the two spring forces, and by exerting a forcebetween the first level and the higher second level, the user can easilykeep the plunger button at the home position. As will be discussed infurther detail below, the ability of the user to identify and maintainthe piston 412 at the home position 610 is a requirement for certaindesirable pipetting operations, both in a hybrid manual-electronicpipette according to the invention and in traditional manual pipettes.

FIGS. 8-10 illustrate the user interface display 126 of a hybridmanual-electronic pipette 110 (FIG. 1) according to the invention whenused in a manner similar to traditional handheld manual pipettes, i.e.in a Traditional Mode.

Initially, and as shown in FIG. 8, the user slides the volume set locklever 244 (FIG. 2) to an unlocked position 246 to allow the pipette 110to be adjusted. The volume set lock lever 244 is equipped with a lockstate switch 2117 (FIG. 21, below) that indicates the state of the lockto a processing unit 2112 (FIG. 21, below) contained in the pipette 110.In an embodiment of the invention, the processing unit comprises alow-power microcontroller capable of running on a small battery for longperiods of time, and further capable of operation in a very-low-power“sleep” state while the pipette 110 is not being used. The MSP430 seriesof ultra-low-power microcontrollers from Texas Instruments Inc. includesintegrated circuits that meet these needs, many of which further provideadditional digital and mixed-signal system-on-a-chip functionality thatcan be advantageously employed in a hybrid manual-electronic pipette 110according to the invention; other vendors also have products that mighteasily be substituted.

In certain operating modes, while the volume set lock lever 244 is inits unlocked position 246, the LCD 230 displays a flashing “UNLOCKED”indication 810 and the currently set volume of the pipette 812, which inthe illustration is 123.6 microliters. By turning the plunger button114, the user can adjust the position of the upper volume-setting stopas in traditional pipettes. However, because the plunger button 114 isspring-biased to its extended position 510 against the adjusted uppervolume-setting stop, the LCD 230 will be updated with the position ofthe piston 412 as it moves with the stop. In any event, any volumereading obtained while adjusting the volume of the pipette 110 can onlybe considered accurate if no longitudinal pressure is being applied tothe plunger button 114.

When the user locks the volume setting by sliding the volume set locklever 244 to the locked position 248, a lock state switch 2117 (FIG. 21,below) actuates, causing the “UNLOCKED” indication to disappear from theLCD 230 and as illustrated in FIG. 9 the LCD 230 displays the fixedvolume setting 910 regardless of the position of the piston 412. Thedisplay 126 is decoupled from the real-time position of the piston 412,allowing the user to determine the capacity of the pipette at a glance,regardless of what stage of pipetting the user is engaged in. Of course,it will be observed that the processing unit still receives measurementsof the position of the piston 412; they are simply not being displayed.

When the volume set lock lever is actuated, an accurate and precisemeasurement is taken of the position of the piston 412 and calibrated bythe processing unit as set forth in greater detail below. Because of thetight coupling among the plunger button 114, the sliding component 416of the position sensing transducer 414, and the air displacement piston412, and further because of the capability of the position sensingtransducer 414 to accurately and precisely read the position of thepiston and of the processing unit to adjust that observed position andapply both linear and non-linear compensation, calibration, andadjustment functions as necessary, this volume reading is consideredmore precise and more accurate than is generally possible using a manualpipette with a mechanical rotary position readout. In particular, theelectronic display is not subject to slack or backlash; furtheradvantages will be detailed below.

During a traditional pipetting operation, there are generally twoprimary actions being performed. First, a sample equal in volume to thesetting of the pipette 110 is picked up, and second, that sample isdispensed or otherwise discharged.

When the plunger button 114 is in the home position 610 before pickingup a liquid, the processing unit observes the corresponding position ofthe piston 412, and as shown in FIG. 10 a “PICKUP” notation 1010 ispresented on the LCD 230 along with the volume setting 1012. Thisprovides visual confirmation to the user that the piston 412 is in thehome position 610 and it is an appropriate time to begin a liquid pickupstroke. It will be noted that numerous other modes of display operationare possible and within the scope of the present invention.

The primary actions of picking up a sample and dispensing it areperformed in the context of a full traditional pipetting cycle, which isillustrated by way of a simple flowchart in FIG. 11.

Initially, the user prepares to pick up a sample (step 1110) by movingthe plunger button 114 to the home position 610. The user notes that thedisplay indicates “PICKUP” 1010 (step 1112). After a brief pause, theuser inserts the tip 116 into the liquid to be handled and aspirates, orpicks up, the sample by gradually releasing (step 1114) the plungerbutton 114 until it reaches its extended position 510. At the conclusionof the aspiration stroke, with the piston released (step 1116), thepipette 110 contains a quantity of liquid equal to the capacitydisplayed on the LCD 230, assuming, of course, that the aspirationstroke was performed correctly.

Then the user moves the pipette 110 over a receptacle and dispenses theliquid sample (step 1118) by gradually pushing the plunger button 114 tothe home position 610. When the piston 412 is at the home position (step1120), a dispensing stroke has been performed, but as is well known inthe art of pipetting small volumes of liquid, some liquid may beundesirably retained in the tip at this stage. Accordingly, the userpushes the plunger button 114 through the home position 610 to a lowerstop, an operation known as “blowing out” the sample, and touches thetip to a surface of the receptacle to remove any last adhering droplet,known as “touching off” (step 1122).

The piston 412 is then in a blowout area (step 1124) below home, withthe plunger button 114 fully depressed 710. To perform another stroke,the user releases some pressure (step 1126) on the plunger button 114 toreturn the piston 412 to the fully extended and released position 510,which requires another return from the extended position to the homeposition to prepare for another aspiration is performed (step 1110).Alternatively, rather than returning to the released position 510, theuser may go back only to the home position 610, in preparation foranother immediate aspiration (step 1110).

Recapitulating to some extent, it will be observed that a traditionalpipetting cycle generally includes an initial stroke to bring the piston412 to the home position 610 (if necessary), pre-aspiration pause at ahome piston position 610, an aspiration stroke, a pre-dispensing pauseat an uppermost piston position, a dispensing stroke, a blowout stroke,and a return stroke (returning to either the home position 610 or thereleased position 510).

A mode of reverse-pipetting is also possible, in which a cycle generallyincludes in initial stroke to bring the piston 412 to its lowermostfully-depressed position 710, a pre-aspiration pause at a lowermostpiston position 710, an aspiration stroke, a pre-dispensing pause at anuppermost released piston position 510, a dispensing stroke, apost-dispensing pause at a home piston position 610, and a blowoutstroke. In this case, the pipette aspirates more than its usual capacityby aspirating during the travel of the piston 412 between the blowoutposition 710 and the home position 610; the dispense stroke includesonly dispensing to the home position 610 and touching off—blowout isdiscarded. The display mode used for reverse-pipetting is identical tothe one used for traditional pipetting

It will further be observed that this sequence of steps is frequentlyperformed many times by a pipette user in the course of a workday, andaccordingly, it is possible for pipetting errors or inaccuracies toarise while repeating the steps. A hybrid manual-electronic pipette 110according to the invention has the unique ability to issue alerts to theuser of improper pipette operating techniques. Such alerts are possiblebecause of the pipette's firmware in conjunction with its ability toaccurately monitor the position of the piston 412 at all times duringoperation. These technique-monitoring capabilities are generally notpossible in traditional pipettes, and will be discussed in furtherdetail below.

Various other advantageous hybrid pipette operating modes are enabled bya hybrid manual-electronic pipette 110 according to the invention.

The traditional pipetting cycle is described above and with reference toFIGS. 8-11. While the electronic readout of volume setting via the LCD230 certainly improves the accuracy and precision of volume-settingoperations, that functionality is generally present (though with reducedaccuracy and precision) in manual pipettes. A function not generallypossible with manual pipettes is Tracking Mode, in which the position ofthe piston 412 is tracked and communicated to the user in real time. TheTracking Mode of pipette operation is illustrated in FIGS. 12-14.

Tracking Mode is accessed by depressing the MODE button 232 until the“TRACK” indication 1210 is displayed on the LCD 230, as illustrated inFIG. 12. Tracking Mode shows the position of the piston 412 on the LCD230 at all relevant times, allowing a user to manually aspirate anddispense as much or as little liquid as desired by maintaining accuratecontrol of the plunger button 114.

In Tracking Mode, with the volume set lock lever 244 is in its unlockedposition 246 (FIG. 2), the LCD 230 shows the real-time position of thepiston 412 in terms of volume 1212, with zero being at the home position610 and the maximum capacity of the pipette being at the fully-releasedposition 510 of the plunger button 114. The “UNLOCKED” indication 1214also flashes.

As set forth in FIG. 13, with the volume set lock lever 244 in itslocked position 248 (FIG. 2), the LCD 230 continues to show thereal-time position of the piston 412 in terms of volume 1310. If theuser wishes, the volume of liquid in the tip 116 at any time can bedetermined by reading a value on the display.

It is neither necessary nor useful to provide details of the position ofthe piston 412 below the home position 610, so when the plunger button114 is in the fully-depressed blowout area 710, the LCD 230 in TrackingMode simply reads “bLo” 1410 (for “blowout,” or “below zero”), asillustrated in FIG. 14.

To summarize, Tracking Mode defines a pipetting cycle comprising anaspiration stroke and a dispensing stroke. Optionally, there may be ablowout stroke following the dispensing stroke. But in general, TrackingMode is considered a relatively freeform mode subject to fewerconstraints than traditional pipetting mode or reverse-pipetting mode.

Similar to Tracking Mode, a Mixing Mode may be available when the onlyaction necessary is to repeatedly pick up and dispense a quantity ofliquid, ensuring that the liquid is sufficiently agitated and mixed.This is even more of a manual mode than Tracking Mode, and although thedisplay may be similar or identical, it may be advantageous to define aseparate Mixing Mode to override any restrictions on aspiration anddispense rates, pauses, or other aspects of the mixing operation thatare not necessary and might give rise to false technique alarms, as willbe discussed in further detail below.

A Titration Mode also allows the position of the piston 412 to betracked and communicated to the user in real time, and is illustrated inFIGS. 15-18. Titration Mode is accessed by depressing the MODE button232 until the “TITRATE” indication 1510 is displayed on the LCD 230, asillustrated in FIG. 15.

Titration Mode is generally used to gradually dispense a quantity ofreagent while observing a reaction or looking for a certaincharacteristic in the vessel into which the liquid is being dispensed.Accordingly, then, Titration Mode advantageously allows the continuousmeasurement of a quantity of liquid as it is being dispensed.

In Titration Mode, with the volume set lock lever 244 is in its unlockedposition 246 (FIG. 2), the LCD 230 shows the real-time position of thepiston 412 in terms of volume 1512, with zero being at the home position610 and the maximum capacity of the pipette being at the fully-releasedposition 510 of the plunger button 114. The “UNLOCKED” indication 1514also flashes.

As set forth in FIG. 16, with the volume set lock lever 244 in itslocked position 248 (FIG. 2), the LCD 230 continues to show thereal-time position of the piston 412 in terms of volume 1610, but withzero set to the fully-released position 510 of the plunger button 114and values between the released position 510 and the home position 610expressed as negative volumes.

Accordingly, then, after a full aspiration stroke, the display 126indicates the quantity of liquid dispensed from the tip 116 as anegative number, starting from zero. While adjusting the volume, thedisplay indicates capacity 1510. At the released position (with thevolume locked), the display 126 indicates zero 1610. In the exemplarydisplay of FIG. 17, the user has depressed the plunger button 114sufficiently to dispense 102.6 microliters 1710 of liquid.

As with Tracking Mode, in Titration Mode it is neither necessary noruseful to provide details of the position of the piston 412 below thehome position 610, so when the plunger button 114 is in thefully-depressed blowout area 710, the LCD 230 in Titration Mode simplyreads “bLo” 1810 (for “blowout,” or “below zero”), as illustrated inFIG. 18.

To recap somewhat, Titration Mode defines a titration pipetting cycleincluding an initial stroke to home position if necessary, followed byan aspiration stroke, a post-aspiration pause at an uppermost pistonposition, a gradual titration dispensing stroke, and a blowout stroke todiscard excess.

Other additional modes of operation are possible in a hybridmanual-electronic pipette 110 according to the invention.

For example, a Transfer Mode is possible in which a cumulative amount offluid dispensed over a multitude of dispense operations is possible. Inthe disclosed embodiment, this mode is accessed by pressing the MODEbutton 232 repeatedly until a “TRANSFER” indication is shown on the LCD230. Additive Mode is similar to Titrate Mode, but where more than asingle dispense stroke may be necessary to achieve the desired reaction.

In Transfer Mode, with the volume set lock lever 244 is in its unlockedposition 246 (FIG. 2), the LCD 230 shows the real-time position of thepiston 412 in terms of volume, with zero being at the home position 610and the maximum capacity of the pipette being at the fully-releasedposition 510 of the plunger button 114. The “UNLOCKED” indication alsoflashes.

With the volume set lock lever 244 in its locked position 248 (FIG. 2),the LCD 230 continues to show the real-time position of the piston 412in terms of volume 1610, but with zero set to the fully-releasedposition 510 of the plunger button 114 and values between the releasedposition 510 and the home position 610 expressed as negative volumes.

Accordingly, then, after a full aspiration stroke, the display 126indicates the quantity of liquid dispensed from the tip 116 as anegative number, starting from zero. While adjusting the volume, thedisplay indicates capacity. At the released position (with the volumelocked), the display 126 indicates zero.

As with Tracking Mode and Titration Mode, it is neither necessary noruseful to provide details of the position of the piston 412 below thehome position 610, so when the plunger button 114 is in thefully-depressed blowout area 710, the LCD 230 in Dilution Mode simplyreads “bLo” (for “blowout,” or “below zero”).

To recap somewhat, Transfer Mode defines a pipetting cycle including aninitial stroke to home position if necessary, followed by an aspirationstroke, a post-aspiration pause at an uppermost piston position, agradual titration dispensing stroke, and a blowout stroke to discardexcess.

After the completion of an initial dispense stroke (and blowout of anyretained liquid), another aspiration stroke and gradual titrationdispensing stroke may be performed. After this subsequent aspiration,the volume reading on the LCD 230 reflects the total dispensed onprevious dispense strokes. For example, if the volume setting is 200microliters, then before the first dispense stroke the volume reading onthe LCD 230 is zero microliters. On the second dispense it is 200microliters, and on subsequent cycles it is increased by 200 microliterseach time. And during the corresponding dispense strokes, the updatedvolume readings reflect the accumulation from previous strokes.

Another function not generally possible with manual pipettes is DilutionMode, in which the pipette is used to pick up known volumes of twodifferent liquids and dispense them both in one stroke.

Dilution Mode is accessed by depressing the MODE button 232 until the“DILUTE” indication is displayed on the LCD 230, or alternatively,Tracking Mode may be used for this operation. As with Tracking Mode,Dilution Mode shows the position of the piston 412 on the LCD 230 at allrelevant times, allowing a user to manually aspirate and dispense asmuch or as little liquid as desired by maintaining accurate control ofthe plunger button 114.

In Tracking Mode, with the volume set lock lever 244 is in its unlockedposition 246 (FIG. 2), the LCD 230 shows the real-time position of thepiston 412 in terms of volume, with zero being at the home position 610and the maximum capacity of the pipette being at the fully-releasedposition 510 of the plunger button 114. The “UNLOCKED” indication alsoflashes.

With the volume set lock lever 244 in its locked position 248 (FIG. 2),the LCD 230 continues to show the real-time position of the piston 412in terms of volume. If the user wishes, the volume of liquid in the tip116 at any time can be determined by reading a value on the display.

It is neither necessary nor useful to provide details of the position ofthe piston 412 below the home position 610, so when the plunger button114 is in the fully-depressed blowout area 710, the LCD 230 in TrackingMode simply reads “bLo” (for “blowout,” or “below zero”).

Generally, a user performs a dilution operation by first performing astroke to home position, then, while watching the LCD 230, graduallyreleases the plunger button 114 until a known desired quantity of adiluent has been picked up. Following that, the user removes the tip 116from the diluent and allows a small air gap to enter the tip 116. Then,while observing the LCD 230, the user will pick up a second known anddesired quantity of a sample. The volume of sample will be reflected bythe difference in the values shown on the LCD 230 between the beginningof the sample pickup stroke and the end of the sample pickup stroke.Both the diluent and the sample may then be discharged and blown out.

To summarize, Dilution Mode defines a single dilution pipetting cyclecomprising an initial stroke to home position if necessary, apre-aspiration pause at a home piston position, a diluent aspirationstroke, a first aspiration pause, an air gap aspiration stroke, a secondaspiration pause, a sample aspiration stroke, a pre-dispensing pause, adispensing stroke, and a blowout stroke.

In Dilution Mode, the display may be identical to that provided inTracking Mode, or alternatively, a means for zeroing the display may beprovided before the sample is aspirated, to allow the sample aspirationto start from zero and eliminate the mental subtraction step otherwiserequired.

Multidispense Mode allows a single sample to be distributed to multiplevessels in multiple small aliquots. In the disclosed embodiment,Multidispense Mode is accessed by pressing the MODE button 232 until“MULTI” is shown on the LCD 230, or alternatively, Tracking Mode orTitration Mode may be used to perform this operation as well. As withTracking Mode, Multidispense Mode shows the position of the piston 412on the LCD 230 at all relevant times, allowing a user to manuallyaspirate and dispense as much or as little liquid as desired bymaintaining accurate control of the plunger button 114.

In Multidispense Mode, with the volume set lock lever 244 is in itsunlocked position 246 (FIG. 2), the LCD 230 shows the real-time positionof the piston 412 in terms of volume, with zero being at the homeposition 610 and the maximum capacity of the pipette being at thefully-released position 510 of the plunger button 114. The “UNLOCKED”indication also flashes.

With the volume set lock lever 244 in its locked position 248 (FIG. 2),the LCD 230 continues to show the real-time position of the piston 412in terms of volume. If the user wishes, the volume of liquid in the tip116 at any time can be determined by reading a value on the display.

It is neither necessary nor useful to provide details of the position ofthe piston 412 below the home position 610, so when the plunger button114 is in the fully-depressed blowout area 710, the LCD 230 in TrackingMode simply reads “bLo” (for “blowout,” or “below zero”).

Generally, a user performs a multidispense operation by first performinga stroke to home position and aspirating a quantity of sample sufficientto cover the desired aliquots plus a small extra amount to ensureaccuracy in the last aliquot. Then, while watching the LCD 230, the usergradually depresses the plunger button 114 until a known desired aliquothas been discharged into a first vessel. Following that, the user movesthe tip to a second vessel and dispenses a second aliquot, and so forthuntil all aliquots have been delivered. The volume of each aliquot willbe reflected by the difference in the values shown on the LCD 230between the beginning and the end of each aliquot dispense stroke. Afterall aliquots have been delivered, any remaining liquid in the pipette110 may be discharged and blown out.

It should be noted that Multidispense Mode accommodates not onlymultiple aliquots of the same volume, but also multiple differingaliquots. Generally, the display in Multidispense Mode is the same as inTitration Mode, requiring the user to note the beginning and endmeasurements for each aliquot dispense stroke, and to perform mentalsubtraction to be sure each aliquot is correct. However, in anembodiment of the invention, the volume displayed on the LCD 230 may bereset to zero following each aliquot dispense stroke, either manually(e.g. via a display reset button) or automatically, which wouldfacilitate ease of use.

In summary, the Multidispense Mode provided by the pipette 110 defines amultidispense pipetting cycle comprising an initial home stroke ifnecessary, a pre-aspiration pause at a home piston position, anaspiration stroke, a pre-dispensing pause, a plurality of aliquotdispensing strokes and dispensing pauses, and a blowout stroke.

Another function not generally possible with manual pipettes isMeasuring Mode, in which the pipette is used to pick up an unknownquantity of a sample and measure its volume.

Measuring Mode is accessed by depressing the MODE button 232 until the“MEASURE” indication is displayed on the LCD 230, or alternatively,Tracking Mode may be used for this operation. As with Tracking Mode,Measuring Mode shows the position of the piston 412 on the LCD 230 atall relevant times, allowing a user to manually aspirate and dispense asmuch or as little liquid as desired by maintaining accurate control ofthe plunger button 114.

In Measuring Mode, with the volume set lock lever 244 is in its unlockedposition 246 (FIG. 2), the LCD 230 shows the real-time position of thepiston 412 in terms of volume, with zero being at the home position 610and the maximum capacity of the pipette being at the fully-releasedposition 510 of the plunger button 114. The “UNLOCKED” indication alsoflashes.

With the volume set lock lever 244 in its locked position 248 (FIG. 2),the LCD 230 continues to show the real-time position of the piston 412in terms of volume. If the user wishes, the volume of liquid in the tip116 at any time can be determined by reading a value on the display.

It is neither necessary nor useful to provide details of the position ofthe piston 412 below the home position 610, so when the plunger button114 is in the fully-depressed blowout area 710, the LCD 230 in TrackingMode simply reads “bLo” (for “blowout,” or “below zero”).

Generally, a user performs a dilution operation by first performing astroke to home position, then, while watching the LCD 230, graduallyreleases the plunger button 114 until the desired quantity of a samplehas been picked up. Without moving the plunger button 114 further, theuser then reads a measurement from the LCD 230 of how much liquid waspicked up. The measured liquid may then be discharged as desired.

Recapitulating, a Measuring Mode pipetting cycle includes an initialhome stroke if necessary, a pause at a home piston position, a measuringaspiration stroke, a post-measuring pause, and a discharge stroke.

It will be further noted that some or all of the foregoing individualpipetting operations may be combined into a complex sequence ofpipetting operations, and a hybrid manual-electronic pipette 110according to the invention may be programmed to facilitate this.

To provide one exemplary scenario, in a relatively complicatedlaboratory experiment, it might be necessary to perform the followingsteps in sequence:

-   -   (1) To first transfer a sample from a sample container into a        first vessel already containing diluent;    -   (2) to then mix the sample and diluent in the first vessel; and    -   (3) finally to then multidispense the diluted sample from the        first vessel into a rack of tubes.

With a hybrid manual-electronic pipette 110 according to the invention,the processing unit may be programmed to perform these steps in sequenceby causing mode switches to occur automatically at the end of eachpipetting cycle, or the stages may be delimited manually.

To elaborate upon the example, initially the pipette would be in thetraditional pipetting mode, and an indication on the display mightinstruct the user to set a specific volume, displaying a message whenthe correct volume is reached. Upon locking the lock lever, the userperforms a traditional pipetting operation to transfer the desiredquantity from the sample container to the mixing vessel.

When the sample is dispensed into the mixing vessel and blown out, theprocessing unit notes that the cycle is complete and then switches intoMixing Mode. The user then performs the desired mixing operation in themixing vessel, and at the conclusion (either indicated by a button pressor by the passage of several seconds from the last stroke, for example),the processing unit then automatically switches to Multidispense Mode,requesting the user to make another volume adjustment, and subsequentlyallowing the user to perform that operation.

To summarize, the Composite Mode defines a sequential plurality ofpipetting cycles selected from traditional cycles, reverse cycles,tracking cycles, titration cycles, dilution cycles, mixing cycles, andmeasuring cycles, and in some of these steps, the pipette maycommunicate specific instructions or reminders to the user, which willbe discussed in additional detail below.

It will be recognized that it is possible that the user may get “out ofsync” with the pipette 110 in Composite Mode (or in any of the otherforegoing modes). It is contemplated that a pipette 110 according to theinvention is able to discriminate between similar strokes (e.g.,aspiration strokes vs. return strokes) by observing the starting andending points, speeds, directions, and if necessary comparable detailsof preceding strokes, to disambiguate the stroke being performed andapply the correct criteria thereto.

It may be burdensome to provide these relatively complex compositeinstructions to the pipette 110 via the built-in user interface 124. Adata interface between the pipette 110 and external equipment may beused to advantage, which will be discussed in further detail below.

In an embodiment of the invention, the user at any time can observe thenumber of full pipetting cycles performed. By pressing the CC button 234(FIG. 2), the number of cycles performed since a reset of the cyclecounter or the initial application of power to the pipette 110 isdisplayed on the LCD 230 as shown in FIG. 19, which by way of exampleshows 35 cycles 1910 having been performed in the traditional pipettingmode, with the capacity set to 26.0 microliters 1912.

Preferably, a hybrid manual-electronic pipette according to theinvention will only count complete pipetting cycles—any incorrectlyperformed or incomplete cycles will be ignored. In the traditionalpipetting mode, for example, a complete cycle comprises: pressing theplunger button 14 to the home position 610, aspirating a sample,dispensing the sample, blowing out the sample (at which point the cyclecounter is incremented), and releasing the plunger back to the releasedposition 510. The processing unit and position sensing transducer 414 ofa pipette according to the invention enable this functionality, which isnot possible with manual pipettes, even those that are capable ofincrementing a mechanical cycle counter.

In the disclosed embodiment, the cycle counter uses three digits to readto a maximum of 999 cycles, after which the counter resets to zero. Thecounter may be manually reset to zero by pressing and holding the CCbutton 234.

As observed above, a hybrid manual-electronic pipette 110 according tothe invention includes an LCD 230, a position sensing transducer 414,and a low-power processing unit, all of which may be powered by abattery. From time to time the battery will require replacement, and asillustrated in FIG. 20, the LCD may include a low-battery indicator 2010which may flash for some time period before battery replacement isrequired. Generally, button-cell batteries such as those used in thedisclosed embodiment of the invention have well-known dischargeprofiles, and it is relatively simple matter to determine an anticipateddischarge from voltage measurements over time.

FIG. 21 is a basic block diagram of an embodiment of the disclosedhybrid manual-electronic pipette 110.

As already discussed, the pipette 110 includes a piston position sensingtransducer 414, illustrated in FIG. 21 as the piston position sensor2110. It also includes a processing unit 2112, which as described aboveis preferably a low-power microcontroller with flexible input/outputcapabilities. With a mixed-signal system-on-a-chip microcontroller asthe processing unit 2112, interfaces to the various other subsystemsdescribed herein (including the piston position sensor 2110) may beeither analog or digital in nature.

The pipette 110 also includes an input panel 2114 (i.e., the buttonpanel 128) and the display 126, generally taking the form of the LCD230. A home position switch 2116 is provided to indicate when the piston412 is in the home position 610, or within a very small positionaltolerance thereof. A lock state switch 2117 is coupled to the volume setlock lever 244, as described above with reference to FIG. 8, and allowsthe processing unit 2112 to determine whether the volume settingmechanism of the pipette 110 is locked or unlocked. As is traditionalwith microcontroller-based devices, sufficient program memory 2118 anddata storage memory 2120 are also provided, and the entire electronicportion of the pipette 110 is powered by a battery as previouslydiscussed.

The power consumption of a pipette 110 according to the invention can beconsiderably mitigated by employing a “sleep mode.” For example, ifsubstantially no piston movement is detected by the piston positionsensor 2110 over three minutes, the pipette may switch to avery-low-power mode and await a wakeup event, such as a processing unitinterrupt triggered by the home position switch 2116. In this way, auser can “wake up” the pipette simply by partially depressing theplunger button 114.

In addition, several other components may be advantageous to include ina hybrid manual-electronic pipette 110 according to the invention. Forexample, a temperature sensor 2122 would enable the processing unit 2112to compensate for liquid characteristics (viscosity, density, etc.)based on environmental temperature. A tip depth sensor 2124 (forexample, an ultrasonic transducer coupled to the liquid end 118) mightprovide advantageous information relating to the depth of the tip when asample is being aspirated. Too shallow, and air may be inadvertentlyadmitted; too deep, and pressure may force additional liquid into thetip.

An inclinometer or accelerometer 2126 may be used to ensure the pipetteuser is following good technique, by keeping the pipette 110substantially upright at all stages of a pipetting operation, withoutabrupt movements or “jerks” that might influence the liquid in thepipette tip 116 or cause contamination in the liquid end 18. Exemplaryinclinometers and accelerometers might include mercury switches todetermine orientation, and electromagnetic flux disturbance or MEMSdevices to determine acceleration.

Actions to be taken in response to poor pipetting technique arediscussed below.

For communicating to the user, in addition to the display 126, thepipette 110 may be provided with an audio transducer 2128 or a tactilefeedback generator 2130. The audio transducer 2128 may “beep” to advisethe user that a certain action needs to be taken or that a problem wasobserved with a preceding pipetting stroke or cycle. In noisy productionor laboratory environments, the “beep” may be replaced by a simplevibratory alert provided by the tactile feedback generator 2130, as iscommonly known from mobile telephones, or a brightly flashing LED may beprovided for a visual alert.

In an embodiment of the invention, the pipette 110 further includes awireless data transceiver 2132 adapted to send and receive informationfrom external devices, such as a workstation 2134 or a server 2136,either of which may be connected to the pipette 110 via a wider networksuch as the Internet or a corporate intranet. A data link 2138facilitated by the transceiver 2132 would allow the pipette 110 to sendstroke or cycle data, or simply only error data, to the external devicefor storage, analysis, or auditing. Such data may be transmitted in realtime as cycles and strokes are performed, or may be stored locally inthe storage memory 2120 of the pipette 110 and downloaded to theworkstation 2134 at a later time.

This data link 2138 would also permit a user of the workstation 2134 todesign a complex program or protocol of pipetting cycles to be performedin a particular sequence, and to upload that program to the pipette 110,as described above.

It will be recognized that the data link 2138 may be realized innumerous ways, including via the Bluetooth, Zigbee, or MICScommunications standards; other approaches are also possible.Alternatively, a wired link such as an RS-232 serial connection or a USBconnection may be provided where a wireless link is impractical (e.g.,in environments where a great deal of electromagnetic noise is present).USB has the further advantage of also being able to supply power to thepipette 110.

A compensation subsystem 2140 is present in the pipette 110, allowingraw measurements taken from the piston position sensor 2110 to beprocessed, adjusted, and compensated as necessary to achieve accurateand precise liquid volume measurements that are presented to the uservia the display 126 and optionally stored in the storage memory 2120 ortransmitted to external equipment 2134. The operation of thecompensation subsystem 2140 will be discussed in further detail below.

Turning now to FIG. 22, the technique analysis capabilities of a pipette110 according to the invention are illustrated with the same sequence ofsteps shown in FIG. 11, which documents a traditional pipetting cycle.

In the traditional pipetting stroke, before and during the initial moveto home position (step 1110), adjustments may be made to the pipettevolume, which will result in movement of the piston 412. Accordingly,these movements are not analyzed for errors.

Subsequently, there is a pause at home position 610, followed by apickup stroke, followed by a pause at released position 510, followed bya dispense stroke, followed by a pause (if any) at the home position,followed by a blowout stroke.

It has been noted that pipetting technique is most important during theinitial pause at home position, the pickup stroke, and the dispensestroke. Consequently, in the disclosed embodiment, at least a pauseanalysis 2210 is performed of that initial pause at home position, apickup stroke analysis 2212 is performed, and a dispense stroke analysis2214 is performed. Optionally, further pause analyses 2216 and 2218 maybe performed following the aspiration stroke and the discharge stroke,and blowout stroke analysis 2220 is performed.

The home position pause analysis 2210 checks to ensure that the homeposition is held stable, in the disclosed embodiment, for at least 0.5seconds. If the pause is shorter, the processing unit 2112 may flag apipetting technique violation. If the pause is shorter still, e.g. lessthan 0.35 seconds, the processing unit 2112 may declare an incompletepipetting cycle in addition to the technique violation.

Similarly, aspirating a sample should be performed at a controlled rateand should start at the home position 610. The aspiration starting pointand the aspiration rate are calculated and checked in the pickup strokeanalysis 2212. If, for example, the aspiration rate (calculated from aplurality of position samples over time) exceeds a threshold, or if theaspiration stroke begins somewhere other than the home position 610, theprocessing unit 2112 may flag a pipetting technique violation. Thisthreshold may depend on the capacity of the pipette and the nature ofthe fluid being pipetted.

Generally, a dispensing stroke has fewer limitations, but it should bechecked for completeness by the dispense stroke analysis 2214. If thestroke is not completed, or it does not start at the released position510, the processing unit 2112 may declare an incomplete pipetting cycleand flag a technique violation.

In an analogous manner, the pause analysis 2216 performed afteraspiration should be at least (for example) 1.4 seconds to avoid apipetting technique violation, or 0.8 seconds to avoid an incompletecycle declaration. And in an embodiment, at least 0.2 seconds should bespent in the blowout position to avoid a technique violation.

If any technique violations occur, an error handler 2222 causes anaction to be performed. A record of a violation may be stored (as a datarecord with or without corresponding stroke data) in the storage memory2120, or transmitted to the workstation 2134. An alert (e.g. a “beep” orvibration alert, or an indication on the display 126) may be provided tothe user. When a violation is stored or transmitted, the data record mayinclude a timestamp, raw stroke data, raw cycle data, cycle count, orany measurements from the components of FIG. 21 that might be relevantto the violation. Various combinations are possible and considered to bewithin the scope of the present invention.

If the pipette 110 has not declared an incomplete cycle, the cyclecounter is incremented 2224 (in some cases, as discussed above, evenwhen a technique violation has been flagged).

FIGS. 23 and 24 provide exemplary displays on the pipette 110 that maybe provided when a violation has been flagged. In FIG. 23, if the homeposition pause analysis 2210 or the pickup stroke analysis 2212 flags aviolation, the LCD 230 may present the message “bAd PICKUP” 2310.Similarly, in FIG. 24, if the dispense stroke analysis 2214, thepost-aspiration pause analysis 2216 or the blowout stroke analysis 2220flags a violation, the LCD 230 may present the message “bAd dSP” 2410 toindicate a problem with the dispensing operation. Other messages,including alternative visual alerts (such as a flashing LED), audioalerts, and tactile alerts are also possible.

It may be desirable, in some circumstances, to use the hybridmanual-electronic pipette 110 without the technique analysiscapabilities in effect—this is particularly true when non-traditionalpipetting techniques and procedures are being used, and many operationswould otherwise be flagged as violations. Accordingly, it is possible todisable the technique analysis by pressing the recessed OPTION button236 and navigating using the MODE button 232 to reach a displayindicating the state of the technique alert. As shown in FIG. 25, whenthe alert is disabled, the LCD 230 reads “ALEr OFF” 2510, and as shownin FIG. 26, when the alert is enabled, the LCD 230 reads “ALEr On” 2610.In the disclosed embodiment, the user may toggle between the twosettings by pressing the CC button 234.

In the disclosed embodiment, the criteria employed to determine whethera technique violation has occurred and whether a cycle should be countedcomprise a plurality of pre-programmed floor (minimum) and ceiling(maximum) criterion values for stroke start positions, end positions,maximum speeds, and pause durations. However, it is also possible toenable user-set criteria, and in an embodiment of the invention, thesecriteria are set by initiating a Learn Mode.

In the Learn Mode, the user performs an exemplary pipetting cycle andrepeats it several times, preferably at least three times. Based onthese exemplary cycles (and building in reasonable tolerances), theprocessing unit 2112 calculates representative maxima and minima valuesthat will be used for subsequent technique analysis. An expert inperforming a particular pipetting operation may perform the exemplarypipetting cycles in Learn Mode, and then give the pipette to aless-experienced user. If the less-experienced user's pipetting variesfrom the expert's example by more than the tolerances, techniqueviolations will be flagged as set forth above. Accordingly, thisfunction of a pipette 110 according to the invention can be a valuableeducational tool, and over a long term can improve quality control.

By using the OPTION button 236 followed by the MODE button 232 tonavigate, a Good Laboratory Practices (“GLP”) counter may be enabled,which counts days between scheduled pipette services. In the disclosedembodiment, four separate modes are possible: GLP1 (one year betweenservices), GLP2 (six months between services), GLP3 (four months betweenservices), GLP4 (three months between services). In FIG. 27, the LCD 230indicates that GLP4 2710 is in effect, with three months betweenscheduled services. The number “37” 2712 indicates that there arethirty-seven days left until the service interval expires.

As the number of days approaches zero, the pipette 110 may providewarnings to the user when turned on or coming out of sleep mode. Ifthere are fewer than thirty days remaining, the display 230 will show a“CAL dUE” message 3710 (FIG. 37), followed by the number of days, e.g.the “14 dAy” message 3810 of FIG. 38. Of course, the GLP counter mode ofthe pipette 110 may also be disabled entirely.

Other timers and counters may also be used, including a GLP counterbased on cycles, or an ergonomic counter based on either cycles orelapsed time. An ergonomic counter according to the invention wouldenable providing alerts to the user suggesting that regular breaks betaken, as repetitive stress injuries may result from extended pipettingsessions using any handheld pipette.

As shown in FIG. 28, a total cycle count since manufacture may beaccessed via the OPTION button 236, followed by multiple presses of theMODE button 232. In the illustration, 12,345 cycles 2810 have beenperformed.

The compensation subsystem 2140 in a hybrid manual-electronic pipette110 according to the invention performs several important measurementcompensation steps, either individually or in combination.

As will be discussed in further detail below, raw measurement signalsfrom the piston position sensor 2110 are not immediately representativeof liquid volumes handled by the pipette 110. Such signals requirecompensation and conversion. These operations are performed by thecompensation subsystem 2140, which in the disclosed embodiment comprisesfirmware routines performed by the processing unit 2112 using at leastone compensation function. As the term is used herein, a “compensationfunction” may include one or more of a zero offset adjustment, a scalefactor, a look-up table, or a mathematical transfer function.

Generally, when hybrid pipettes according to the invention aremanufactured, there are at least two sources of inaccuracy inmeasurement. First, signals from the piston position sensor 2110 may notbe linear. Second, even after linearization of the piston position, theconversion to liquid volume is somewhat non-linear.

Sensor non-linearity is often a function of manufacturing variances, andaccordingly, in a disclosed embodiment of the invention, a sensorposition compensation function (e.g., in the disclosed embodiment, asensor linearization table) is generated on a pipette-specific basis. Aseach pipette comes out of manufacturing, it is placed on a calibrationfixture that runs the piston 412 through its entire range of motion andidentifies any differences between the measurement observed by thepiston position sensor 2110 of the pipette 110 and the known measurementof the calibration fixture. Any deviations are used to create a look-uptable, so that given a measurement from the position sensor 2110 (andextrinsic information as necessary), the correct linear displacement canbe calculated via a simple look-up translation.

Liquid volume corrections are further necessary and borne out of liquidcharacteristics such as density, volume, surface tension, viscosity, tipgeometry, and tip material. Assuming distilled water at room temperatureas the ideal liquid, and the use of a standard tip in a standardconfiguration, any liquid volume corrections generally do not changewith respect to manufacturing variances, but rather are dependent on theknown characteristics of a specific model of the pipette liquid end 118.Accordingly, a volume compensation function (e.g., in the disclosedembodiment, a liquid value correction table) is generated off-line by asequence of balance measurements of pipetted liquid, and once thisfunction is established, it can apply to all pipettes using the sameliquid end configuration. Following linearization of the pistonposition, these corrections are also applied by a simple table look-uptranslation.

Other corrections and adjustments are, of course, possible, and it willbe noted that other methods (such as curve-fitting mathematicalfunctions to the data and applying those functions as a transferfunctions, or in the simplest example, using only offsets and scalefactors) would also achieve comparable results. Moreover, it is possibleto combine the sensor linearization table and the liquid volumecompensation table into a single table or function, so that only onetranslation needs to be applied; this is deemed equivalent to thedescribed embodiment. Similarly, implementing the calibration subsystem2140 outside of the processing unit 2112, or by other methods, is alsoachievable by engineers of ordinary skill, so the disclosed embodimentis deemed merely representative.

A user-calibration option allows a user to toggle a user-calibrationfunction between the factory default calibration setting used by thecompensation subsystem described above and a custom user calibrationsetting (i.e., turning the user calibration constants on and off,provided user calibration data exists.) As illustrated in FIG. 32, whenthe user-calibration function is enabled, the “U-CAL” symbol 3210 willbe displayed on the display 126 at all times during operation of thehybrid manual-electronic pipette 110 (FIG. 1). User-calibration datawill be applied after the foregoing sensor linearization and liquidvolume corrections have been applied.

Referring now to FIG. 29, user-calibration settings are accessed onceagain by depressing the OPTION button 236 followed by multiple pressesof the MODE button 232 until “UCAL” 2910 appears in the display. Ifthere is no user calibration data in the user-calibration table of thecompensation subsystem (which is the factory default for a new pipette)“UCAL” 2910 will be displayed in the volume digits, followed by “---”2912, the U-CAL symbol 3310 (FIG. 33) will not be displayed, and the CCbutton 234, which is ordinarily used to toggle user-calibration on andoff, will have no action since there is no user calibration datapresent. If user-calibration data is present, “UCAL ON” or “UCAL OFF”will be displayed, and the CC button 234 will toggle between the two.

Pressing the MODE button 232 will advance the display to theuser-calibration setting option. As shown in FIG. 30, when this optionis being used, the LCD 230 reads “UCAL SET” 3010. If the user wishes toenter calibration data for the current volume setting of the pipette hesimply presses the CC button 234 while the UCAL OPTION option window isdisplayed; pressing the CC key 234 will cause the display to show thecurrent volume setting 3310 (not flashing) along with a flashing U-CALsymbol 3312, as illustrated in FIG. 33. The CC digits will then displayeither “Inc” 3314 or “dEc” 3410 (FIG. 34), which indicates the directionthat the MODE button 232 will change (correct) the displayed volume. Thedirection can be toggled to the opposite direction by pressing the CCbutton 234. By using both the MODE button 232 and the CC button 234,user can change the displayed volume so that it displays the actualvolume dispensed at the current setting. When the displayed volume ischanged to anything other than its original setting (before theuser-calibration data entry mode is selected) it is also flashed alongwith the U-CAL symbol 3312, which indicates to the user that it has beenmodified but not entered yet. When the user has the correct volumedisplayed he can enter it into the user-calibration table by pressingthe recessed OPTION button 236.

By correctly following the above procedure the pipette will then confirmthat the user-calibration entry was successful by displaying the U-CALsymbol 3510 and “donE” 3512 in the volume digits (FIG. 35) brieflybefore it automatically goes back to the previous display mode with theuser-calibration feature turned on, indicated by the U-CAL symbol beingdisplayed. Additional user-calibration data points can then be enteredby repeating the steps above—first adjusting the pipette to the desiredvolume, then incrementing or decrementing the displayed value, thenpressing the OPTION button 236 to store it. If the plunger is movedduring any of the incrementing or decrementing steps outlined abovebefore the final press of the OPTION button 236, the user-calibrationdata entry is immediately aborted and the pipette returns to normaloperation. The attempted calibration entry will be ignored and an errormessage will be displayed on the LCD 230.

The shaft lock must be in the locked position during the entireuser-calibration setting procedure. If the shaft lock is in the unlockedposition when user-calibration setting is activated with a CC button 234press, or if it is unlocked later during the procedure, an error messageis displayed and the pipette will not permit the calibration to beperformed.

A user-calibration clear function is available and is accessed bypressing the OPTION button 236, followed by the MODE button 232 until,as shown in FIG. 31, “UCAL CLr” 3110 is displayed on the LCD 230. Thisfunction is only available if user-calibration data was previouslycreated; actuating it will delete all the user-entered calibrationpoints, and restart calibration over from factory-default values.

To clear a user-calibration table using the user-calibration clearfunction, the user must first press the CC button 234 to select theclear function. The display then shows the U-CAL symbol, “CLr”, and aflashing “no”. The user then must press the CC button 234 again toconfirm the operation, at which point “YES” will appear, and hold the CCbutton 234 for a few seconds longer to perform the clear operation. TheLCD 230 will momentarily display the U-CAL symbol along with “CLrd”before returning to normal pipette operation with the U-CAL symbol off,confirming the successful clearing of the user-calibration table. Thedefault factory calibration constants will not be affected by thisaction.

If the above procedure is not followed properly the user-calibrationclear function will be aborted without the table being cleared. Theclear function is purposely made to be a little more complex thannecessary to help prevent an accidental clearing by a user justexploring the user interface or making an inadvertent button selection.An aborted user-calibration clear function can easily be detected by afailure to see the confirmation message in the LCD 230, or by noticingthat the U-CAL on/off window is still active, or that the U-CAL CLroption is still listed in the menu.

Using only one user-calibration volume setting to calibrate the pipettesimply adds a single offset to the factory default calibrationconstants. A user can add additional points (volume settings) to get abetter calibration over the full range of the pipette.

In the disclosed embodiment, more than one calibration volume settingwill automatically use a straight-line connection between calibrationvolumes for correction values to volumes between the calibration points.Each point is added in a manner similar to the first point describedabove. The full-scale range of a pipette is divided into 50, 64, 75, or80 equal segments, depending on the range of the pipette, forcalibration purposes. Each of these segments has a unique correctionconstant that is calculated via linear interpolation from the usercalibration volumes, though other interpolation schemes are certainlypossible. Therefore, a user can theoretically add up to 50, or more,separate calibration points to the custom user calibration table if hedesires. Above and below the user-set anchor points, constant offsetsare used reflecting the offsets present at the uppermost point and thelowermost point.

In an embodiment of the invention, a second user calibration point wouldcause the pipette to use a straight-line correction over its entirerange, provided that the two calibration volumes are separated enough;that is, a calibration slope as well as an offset would be applied inaddition to the factory default constants. If only one calibrationvolume was measured a user could force it to be a slope correction,rather than just an offset correction, by setting the pipette volume toits lowest value and performing a second calibration entry with zero, orvery small, correction made to the volume reading. This second entrywould not require an actual measurement.

FIG. 36 illustrates one possible user-calibration scenario in a 200microliter pipette according to the invention. As shown, four anchorpoints are entered:

-   -   (1) At 75 microliters, a first adjustment point 3610 is added so        the pipette display will read 65 microliters;    -   (2) At 100 microliters, a second adjustment point 3612 is added        so the pipette display will read 120 microliters;    -   (3) At 50 microliters, a third adjustment point 3614 is set at        the default value, so 50 microliters is read on the display; and    -   (4) At 150 microliters, a fourth adjustment point 3616 is set at        the default value, so 150 microliters is read on the display.

Accordingly, then, five segments are calculated using the four points.From zero to the first point 3610 at 50 measured microliters, theoriginal calibration is used, because the defaults are present at bothzero and 50 microliters. Between 50 and the second point 3612 at 75measured microliters, adjusted values are used to fit a line segmentbetween a reading of 50 microliters at 50 measured microliters, and areading of 65 microliters at 75 measured microliters. Similarly, between75 and the third point 3614 at 100 measured microliters, adjusted valuesare used to fit a line segment between a reading of 65 microliters at 75measured microliters, and 120 microliters at 100 measured microliters.Between 100 and the fourth point 3616 at 150 measured microliters,adjusted values are used to fit a line segment between a reading of 120microliters at 100 measured microliters and the default of 150microliters at 150 measured microliters. Finally, between 150microliters and the maximum capacity, the original calibration is used(the offset on the final segment is zero, because the offset is zero at150 microliters). As with the sensor linearization and liquid volumecorrections described above, the use of an interpolated table permits asimple and fast table look-up operation to apply the user-calibrationdata in a pipette 110 according to the invention.

To increase the accuracy of any given adjustment point a user shouldfirst average a number of measurements, made at the same volume setting,before entering the measured average volume as the pipette calibrationvolume. If a pipette calibration volume falls into the same segment thata previous calibration volume had then the latest entry will simplereplace (supersedes) the previous entry; in other words, the pipettedoes not average calibration volumes made in the same segment (tableposition or interval.) The user must average volume measurements, at thesame volume setting, first before initiating a user-calibration entry ata given volume setting.

The above approach assumes that a user takes calibration measurementsfor one volume setting at a time and enters the correct volume for thatsetting into the pipette before collecting data on another volumesetting. If a user prefers to take calibration measurements at allvolumes before entering the data into the pipette then the user mustfirst convert a user's set of measurements into a set of calibrationcorrections and the order that they must be entered into the pipette. Inmany cases taking all the calibration data at once before entering maybe more convenient and also may result in a more accurate usercalibration.

The actual value of the calibration correction should not exceed apredefined maximum volume. If a user enters a volume which exceeds themaximum limit the pipette will signal an error condition.

The volume measurement displayed on the LCD 230 of a pipette 110according to the invention will frequently take into account a rawmeasurement from the piston position sensor 2110, as adjusted by thesensor linearization table, the liquid volume correction table, and theuser calibration table (if any). It should be further noted that othercorrection steps may also be necessary, and in correcting the liquidvolume measurements, an additional correction table based on anunforeseen manufacturing variance (unrelated to sensor linearization)might also be necessary. Accordingly, a manufacturing correction tablemay also be used in a similar manner to the other tables described atlength, though in most cases, for most pipettes, it should not benecessary.

It will be noted that various types of piston position sensors 2110 arepossible, and in fact, several versions of a position sensing transducer414 are listed in the description, above, of FIG. 4.

Considering the situation in more detail, a digital optical positionsensing transducer 3910 is illustrated schematically in FIG. 39. Asillustrated, the optical position sensing transducer 3910 includes fixedfirst and second emitters 3912 and 3914 and fixed first and seconddetectors 3916 and 3918, between which is a sliding transparent opticalscale 3920 marked with a code track 3922. As the scale 3920 movesbetween the emitters 3912-14 and the detectors 3916-18, the code trackinterrupts the transmission of light. The emitters 3912-14 andcorresponding detectors 3916-18 are offset slightly, such that movementof the scale 3916 in a first direction results in interruption of thepath between the first emitter 3912 and the first detector 3916 slightlybefore interruption of the path between the second emitter 3914 and thesecond detector 3918. Conversely, movement of the scale in the oppositedirection results in interruption of the path between the second emitter3914 and the second detector 3918 slightly before interruption of thepath between the first emitter 3912 and the first detector 3916. In thisway, the processing unit 2112 can determine the direction of movement,and by counting interruptions, can determine the distance of movement aswell. This scheme is well known and is described in detail in U.S. Pat.No. 6,313,460 owned by Siemens AG of Germany, issued on Nov. 6, 2001,which is hereby incorporated by reference as though set forth in full,and in numerous other patents and publications.

It will be noted that optical encoders such as the one described abovesuffer from some significant disadvantages. Specifically, goodperformance requires that the optical track be kept clean andtransparent, and contamination might compromise this. Moreover, asignificant amount of power is needed for the emitters 3912-14, and arelatively fast processor is needed at all times to count pulses anddetermine how much movement has occurred.

FIG. 40 illustrates the basic components of an inductive positionsensor, as described in U.S. Pat. No. 6,005,387 owned by Mitutoyo Corp.of Japan, issued on Dec. 21, 1999, which is hereby incorporated byreference as though set forth in full, and in numerous other patents andpublications. The inductive position sensor includes a fixed transceiverboard 4010 with two transmission coils 4012 and 4014, and a separatepair of overlaid receiver coils 4016, configured in quadrature. Theinductive position sensor further includes a sliding flag board 4018with passive coupling coils thereon. By selectively energizing thetransmission coils 4014 and 4014, and observing signals at the receivercoils 4016 (which depend on the relative phase of coupling accomplishedby the coupling coils), the relative position between the transceiverboard 4010 and the flag board 4018 can be determined.

FIG. 41 illustrates a capacitive position sensor, as described in U.S.Pat. No. 4,882,536 to Meyer of Switzerland, issued on Nov. 21, 1989,which is hereby incorporated by reference as though set forth in full,and in numerous other patents and publications. In this case, a fixedtransceiver board 4110 includes several charge-storing plates, a firstset 4112 and a second set 4114, with all plates in a set connected toeach other. A sliding coupling board 4116 includes severalinterconnected conductive charge-coupling plates 4118. As thecharge-coupling plates 4118 pass to varying degrees over thecharge-storing plates 4112 and 4114, the transceiver board 4110 and thecoupling board 4116 together form a variable capacitor, which can affectthe characteristics of a tuned circuit in a measurable and highlyreproducible way. Accordingly, the amount of overlap can be accuratelyand precisely determined.

There are, of course, other kinds of sensors that can be used in ahybrid manual-electronic pipette according to the invention, includingdigital contact code-track sensors and potentiometers (which are subjectto wear and tear), and rotary encoders connected via a linkageconverting linear motion to rotary, such as a rack and pinion gear(which would be subject to undesirable slack and backlash). Magneticfield sensors (such as Hall Effect or GMR sensors) may also be used withsatisfactory results.

It should be noted that an inductive and capacitive sensors of the sortdescribed in U.S. Pat. No. 6,005,387 and (referenced above) are relativeposition sensors only, with signals that repeat periodically over thefull course of travel of the flag board 4018 (and hence the piston 412).Whereas position within a single cycle can be determined with greataccuracy, overall position cannot. Consequently, some other mechanism isneeded to determine which cycle out of several the piston 412 ispositioned within. In an embodiment of the invention, the processingunit 2112 generally samples the signal from the piston position sensor2110 at a relatively low sample rate, for example, around 330 Hz. Ifrapid movement is determined at any time using this low sample rate,then a higher sampling rate (e.g. 2 kHz) is employed until the positionsettles. If a transition between otherwise identical cycles (or“quadrants” in the quadrature scheme) is observed, a separate quadrantcount is updated as necessary to maintain an absolute positionmeasurement.

For example using the inductive sensor scheme described above andillustrated in FIG. 40, an arctangent table would ordinarily be used toturn the quadrature signals from the receiver coils 4016 into a linearposition. As the arctangent function repeats every 180 degrees, thequadrant count is used to ensure absolute position is trackedaccurately. Moreover, because of manufacturing variances, even thearctangent table is not a precise mapping of signal level toposition—the sensor linearization procedure described above will“distort” the arctangent table to account for any observednonlinearities.

FIG. 42 sets forth an overview of the steps performed by the processingunit 2112 in a hybrid manual-electronic pipette 110 according to theinvention. In general, the pipette 110 operates in a continuous loop,with some operations occurring in parallel with others, and certainoperations being event-driven (based on signals from various componentsillustrated in FIG. 21) rather than procedurally determinative, but theillustration of FIG. 42 and the description set forth herein arerepresentative in nature. Other comparable implementations areconsidered to be within the scope of the invention.

Initially the processing unit 2112 receives a raw (uncorrected) positionmeasurement by way of a sensor signal 4210 obtained from the pistonposition sensor 2110 (step 4212). As described above, the actualposition of the piston 412 is corrected by applying a compensationfunction (step 4214), and in the disclosed embodiment of the invention,a piston compensation look-up table 4216 is employed, which is obtainedfrom a post-manufacturing displacement calibration operation, as it mayvary from pipette to pipette. For a relative position sensor such as thecapacitive or inductive sensors described above, a more detaileddescription of the position compensation function (step 4214) isdescribed below with reference to FIG. 43.

After the position of the piston 412 has been calculated, a liquidcorrection function is applied (step 4218). As described above, in thedisclosed embodiment of the invention, a liquid correction table 4220used to perform this correction is substantially invariant from pipetteto pipette, provided a standard (idealized) liquid end and tipconfiguration is used.

Optionally, an additional manufacturing adjustment is performed (step4222) based on a manufacturing adjustment table 4224. As describedabove, after piston compensation and liquid correction operations areperformed, if any inaccuracies or inconsistencies remain, themanufacturing adjustment table 4224 may be generated to correct theseinaccuracies and inconsistencies, but in the disclosed embodiment it maynot be necessary to apply this correction. In this case, themanufacturing adjustment table 4224 may not exist, or if it does it maybe populated with zero values (representing zero offset at allmeasurements, which is the same as not performing any manufacturingadjustment function).

Following manufacturing adjustment, if any, a user calibration functionmay be applied (step 4226) if a user calibration table 4228 is present.As discussed above, user calibration data in the user calibration table4228 is also optional, and may be either entered by the user interface124 or transferred via the data link 2138 to the pipette 110.

In the disclosed embodiment, the liquid correction, manufacturingadjustment, and user calibration functions 4218, 4222, and 4226 are allperformed via a simple look-up table operation, in which thepre-correction data is used as an index into the look-up table, and datain the table is used as a simple additive offset as illustrated in FIG.45, described below. This is a fast and simple operation even forlow-power microcontrollers having a limited feature set, and hence, itis considered advantageous to implement the functions in this manner.However, other methods of applying correction functions are well knownand may be used as alternatives to the look-up tables described herein.

Following all of the compensation, correction, adjustment, andcalibration functions, the user's pipetting technique is analyzed duringthe stroke being performed (step 4230). Stroke analysis (step 4230) isdescribed below and illustrated in FIG. 46; this analysis functiongenerally uses the position of the piston 412 (from step 4214) and theposition 4232 of the volume set lock state switch 2117 asinputs—technique analysis is disabled while the volume set lock lever244 is unlocked.

The user interface 124 of the pipette 110 is then updated as appropriatewith computed display contents (step 4234), including signaling the userof any technique violation errors that might have occurred (via the LCD230, an LED, the audio transducer 2128, or the tactile feedbackgenerator 2130, for example). As various pipetting display modesdescribed above call for volume to be displayed, the volume iscalculated based on the compensated, corrected, adjusted, and calibrateddata obtained originally from the sensor 2110. It should be noted thatthe conversion from linear displacement units to volume may take placeat any stage. In the disclosed embodiment, it occurs only when a valueneeds to be displayed, and all of the foregoing data-processingfunctions operate in terms of (arbitrary) linear displacement units tomaintain maximum precision. However, at the time of display, theconversion is made (generally by multiplying by a known constant basedon the liquid end 118 being used) and the position of a zero point,which is dependent on the pipetting display mode 4236 currently in use.

Any data records are logged as necessary (step 4238), which may dependon the presence or absence of technique violation errors or movement ofthe piston 412, and this process repeats in a loop as necessary.

As indicated above, the sensor signal compensation function of FIG. 42is described in more detail with reference to FIG. 43. This function isemployed when a relative position sensing technology is used, such asthe capacitive or inductive sensors illustrated in FIGS. 40-41.

In the disclosed embodiment in which an inductive sensor is used, aftera sensor signal is read (step 4310) from the sensor 2110, a relativeposition is determined (step 4312) based on an averaged plurality ofsamples of the sensor signal and an adjusted arctangent table 4314,which as described above is generated from an initial sensor calibrationoperation performed after the pipette 110 is manufactured. Thearctangent function is used to convert two signals in quadrature (i.e.,a Signal 1 and a Signal 2) obtained from the receiver coils 4016 into aknown position within a quadrant—and the entire range of travel for thepiston 412 is divided into a plurality of quadrants, as described aboveand illustrated in the following table:

Quadrant: 1 2 3 4 5 6 7 Angle: 0-90 90-180 1 80-270 270-360 360-440440-530 530-620 degrees degrees degrees degrees degrees degrees degreesSignal 1 + + − − + + − polarity: Signal 2 − + + − − + + polarity:

If the piston 412 appears to be near a boundary between two adjacentquadrants (step 4316), that is, when either Signal 1 or Signal 2 issufficiently close to a zero-crossing, further inquiry is necessary. Asdescribed above, the sample rate is increased (step 4318) if the speedof movement of the piston 412 exceeds a threshold. In the disclosedembodiment, the sensor signal sampling rate is increased from 330 Hz to2 kHz as necessary to identify all zero-crossings in either Signal 1 orSignal 2.

From an observation of the table above, it will be apparent that basedonly on the Signal 1 and Signal 2 values, there is potential ambiguitywith respect to the absolute position of the piston 412. For example,Quadrant 1 and Quadrant 5 exhibit the same signal characteristics, as doQuadrants 2 and 6. Accordingly, the increased sample rate set forthabove ensures that quadrant changes are always successfully tracked(step 4320) in a pipette 110 according to the invention. A quadrantcount is updated (step 4322) as necessary to disambiguate the positionof the piston 412. Based on the relative position calculated at step4312 and the quadrant count 4324 (updated as necessary at step 4322), anabsolute position of the piston 412 is calculated (step 4326) in aprecise and accurate manner, even when the plunger button 114 is movedvery rapidly.

It will further be recognized that Signal 1 and Signal 2 approximatesine and cosine functions in an inductive sensor as illustrated in FIG.40, and accordingly, the appropriate function to convert theiramplitudes to a position is the arctangent, as illustrated in FIG. 44.In other words, the ratio between Signal 1 and Signal 2 is used tocalculate the position. After the ratio of the two processed analogsignals is taken, a lookup table is used to determine the arctangent,scaled to a desired range. As stated earlier, the arctangent function isthe ideal function; in reality, due to the actual layout of the positiontransducer circuit board and other physical factors, the compensationtable 4314 will require slight modifications to obtain the bestaccuracy. This table will be empirically determined for each pipetteimmediately following manufacture, on an automated fixture.

The operations employed by a pipette 110 according to the invention toapply liquid correction, manufacturing adjustment, and user calibrationfunctions (performed in FIG. 42) are all described with reference toFIG. 45. An uncorrected value is read (step 4510) and used as an indexinto a look-up table 4512, such that the full range of the pipette 110maps to the size of the look-up table 4512. There need not be one-to-onemapping between positions of the piston 412 and the size of the look-uptable 4512; the mapping may cause a single table entry to be applied tomultiple adjacent uncorrected values. As set forth above, the table 4512may contain 50, 64, 75, or 80 values in the disclosed embodiment, whilethe uncorrected position and volume values used for calculation have amuch finer resolution, on the order of thousands of possible values.

The table 4512 includes a list of offset values—the appropriate value isread (step 4514) and the offset stored in the table, which may be apositive or negative value, is added (step 4516) to the uncorrectedvalue to obtain the result.

FIG. 46, as noted above, illustrates an exemplary procedure performed bythe technique analysis function of a pipette 110 according to theinvention. This function may employ a plurality of measured parameters(step 4610) obtained from various measurement components (as illustratedin FIG. 21) in an embodiment of the invention. Specifically, theposition of the plunger 412, the direction of the plunger's movement,the speed of the plunger's movement, and a timer are particularlyessential to the illustrated version of the technique analysis function.It will be recognized, of course, that other implementations of atechnique analysis and verification function may be employed and areconsidered within the scope of the present invention.

As described above, piston movement speeds and pause lengths areparticularly important measurements. Accordingly, the illustratedprocedure initially determines whether the piston 412 is moving (step4612). If it is not moving, a running count representing a pause lengthis updated (step 4614), and nothing else is done.

If the piston 412 is moving, and it previously was not in motion, orpaused (step 4616), then an appropriate pause criterion selected from alist of criteria 4618 is checked (step 4620). For example, as describedabove, a minimum pause duration at a released position may be 0.8seconds. There may be pause criteria only for certain locations, andonly with respect to certain strokes or cycles; this may vary based onthe pipette operating mode as described above. If the pause criterion isnot met, a violation is flagged (step 4622). If it is met, the pauselength is reset (step 4624) because the piston 412 is moving again, andno error results (step 4626).

If the piston 412 is moving and it was previously in motion (notpaused), then the piston direction is identified (step 4628), forexample, by noting the polarity of the difference between two successivepiston positions. The piston speed is also calculated (step 4630), forexample, by noting the magnitude of the difference between twosuccessive piston positions. The stroke is then identified (step 4632),based on the calculated direction and speed, a history of previousstrokes performed, and a stored list of expected stroke sequences 4634depending on the pipette operating mode.

Based on the identified stroke and the pipette operating mode, one ormore movement criteria in the list of technique criteria 4618 may bechecked (step 4636), for example a maximum permitted stroke speed duringaspiration. And as with pause lengths, if the criterion is not met, aviolation is flagged (step 4638). If the movement of the piston 412 iswithin permissible bounds, no error is noted (step 4640).

In an embodiment of the invention, power savings are facilitated byenabling a sleep mode when the pipette 110 is not being used. If, whileperforming the procedure of FIG. 46, a pause length (updated at step4614) without substantial movement of the piston 412 exceeds a largevalue, such as three minutes, sleep mode may be activated. In thedisclosed embodiment, sleep mode is disabled upon receipt by theprocessing unit 2112 of an interrupt caused by the home position switch2116. Accordingly, then, a user may bring a pipette 110 according to theinvention out of sleep mode simply by depressing the plunger button 114to home position 610.

It should be observed that while the foregoing detailed description ofvarious embodiments of the present invention is set forth in somedetail, the invention is not limited to those details and hybridmanual-electronic pipette made according to the invention can differfrom the disclosed embodiments in numerous ways. In particular, it willbe appreciated that embodiments of the present invention may be employedin many different fluid-handling applications. It will be appreciatedthat the functions disclosed herein as being performed by hardware andsoftware, respectively, may be performed differently in an alternativeembodiment. It should be further noted that functional distinctions aremade above for purposes of explanation and clarity; structuraldistinctions in a system or method according to the invention may not bedrawn along the same boundaries. Hence, the appropriate scope hereof isdeemed to be in accordance with the claims as set forth below.

1. A hybrid manual-electronic pipette operative to handle a fluid, thepipette comprising: a piston assembly comprising a manually operatedpiston and an electronic sensor coupled to the piston; a fluid-tightliquid end receiving the piston and defining a distal opening permittingfluid to be picked up or discharged therethrough in response to movementof the piston within the liquid end; a processing unit coupled toreceive at least one measurement from the electronic sensor, wherein themeasurement relates to a pipetting operation performed by a user of thepipette; and a memory subsystem adapted to store at least one datarecord including a parameter representative of the measurement.
 2. Thehybrid pipette of claim 1, wherein the pipetting operation comprises oneof: an aspiration stroke, a dispense stroke, a pause before aspiration,a pause after aspiration, a blowout stroke, a pause after blowout, amixing stroke, or a titration stroke.
 3. The hybrid pipette of claim 1,wherein the electronic sensor comprises at least one of a pistonposition sensor, a liquid volume sensor, a piston speed sensor, apipette orientation sensor, an accelerometer, or a tip depth sensor. 4.The hybrid pipette of claim 3, wherein the electronic sensor is a pistonposition sensor comprising one of: a variable resistor, an opticalsensor, a capacitive sensor, an inductive sensor, or a magnetic fieldsensor.
 5. The hybrid pipette of claim 1, wherein the data recordfurther comprises at least one of: a time stamp or a stroke number. 6.The hybrid pipette of claim 1, wherein the parameter comprises at leastone of: a pause duration at a home position preceding an aspirationstroke; a pause duration at an upper stop following an aspirationstroke; a pause duration following a blowout stroke; a minimum, maximum,or average piston speed during an aspiration stroke; a minimum, maximum,or average piston speed during a dispensing stroke; a minimum, maximum,or average piston speed during a blowout stroke; an aspiration strokestarting location; an aspiration stroke ending location; a dispensingstroke ending location; a stroke direction at a specified strokelocation; or a stroke speed at a specified stroke location.
 7. Thehybrid pipette of claim 1, further comprising a transceiver operative totransmit the data record to an external device.
 8. The hybrid pipette ofclaim 7, wherein the transceiver enables a wireless data link betweenthe pipette and the external device.